The growth of Internet and wireless communications promises to give people the ability to send and receive voice, data and video messages from/to a number of different wired and wireless devices. One of the challenges faced by traditional telephone companies and new entrants in the communications field (collectively referred to herein as “service providers”) is how to provide satisfactory service to their customers when such customers travel or “roam” from one kind of network to another. Subscribers would like to be reachable in any network when a caller or so-called “session initiators” attempt to reach them using any one of their “network identities” (e.g., email address, Session Initiation Protocol (SIP)-Uniform Resource Locator (URL), directory number, etc. . . . ) or contact addresses that is not necessarily intrinsic to the network they are presently roaming in. For example, a user is reachable at her cell phone when a caller attempts to initiate a session to the user's IP-based identity or contact address. The ability to offer so-called “seamless, global roaming” is a high priority among national and international service providers.
The ability to provide IP-based voice, video and instant messaging services promises increasing revenues to service providers. Standards for such services have evolved over time. Presently organizations like the 3rd Generation Project Partnership (3GPP) and 3rd Generation Project Partnership 2 (3GPP2) design such networks based on the popular Internet Engineering Taskforce (IETF) Session Initiation Protocol (SIP). These networks are known by similar terms such as IP Multimedia Core Network (IMCN), IP Multimedia Subsystem (IMS) or all-IP networks. In order to provide seamless global roaming there is a need for techniques that allow for the establishment of a communication session across disparate networks independent of the network to which a user of an originating message belongs to.
Thus, there is a need in the art for techniques that provide seamless global roaming to users who use multiple identities or contact addresses or who operate devices in all-IP networks or in different networks using different protocols.